Final Thoughts

Hello Everyone!

Reflecting on my research goals for the summer, I have now completed a library of spectra with surface enhanced Raman spectroscopy of a collection of organic yellow dyes and pigments.  Now, I could hypothetically identify an unknown organic yellow colorant in a historical oil painting by sampling only a fraction of what would be needed for other, less sensitive techniques.  The only dye I was not able to identify with SERS was gamboge, which is made of a resinous material that is insoluble and very difficult to work with.  However, gamboge was frequently used in historical paintings, so it is important that I am able to develop a pre-treatment strategy that works for it in the future.  So far I have been able to solubilize it in a solution of ethanol and water, but this treatment has not yielded clearer spectra so far.

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Make Your Own Oil Paint!

Hi Everyone,

The end goal of my summer research was to prepare a comprehensive library of SERS spectra for the many possible plant sources of organic yellow dyes and pigments.  Once I tested the water soluble, cooperative dyes and extracted the insoluble pigments, the next step was to test oil paints.  As the pigments and dyes would be found on a painting mixed with an oil binder, the best simulation of an art sample would be to take SERS spectra of oil paints made from the yellows I have been testing.

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Under the Surface of a Painting

Hello again!

Due to our collaboration with Shelley Svoboda at the Dewitt Wallace Collections and Conservation building, my lab has access to historical oil paintings to sample and study.  Currently, the piece of interest in my project is the portrait of Mrs. Nelson by Robert Feke, an American artist.  Despite the fact that the subject of the portrait is wearing a blue dress, yellows may be hiding among the paint layers.

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Why are the trees blue?

Hello Everyone!

Over the past few weeks I have been working towards perfecting a procedure to simulate surface enhanced Raman spectroscopy of an organic yellow art sample.  Many organic yellow dyes produce beautiful SERS spectra with the traditional procedure, involving the coating of a minute sample with centrifuged silver nanoparticles and shooting a laser beam directly onto the particle.  However, lake pigments involve the mordanting of a dye with an inorganic binding medium, making it difficult for the silver nanoparticles to interact properly with the surface of the dye molecules and produce accurate spectra.

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And It Was All Yellow

Hello again!

Over the past few weeks I have spent most of my time familiarizing myself with different types of yellow dyes and pigments, learning about historic methods of paint making and sifting through the chemistry behind organic yellows.  I can safely say I will never look at the color yellow the same way again.  Despite the hours spent separating minute samples of these colorants, I find the engagement with color to be a fascinating and enriching process.  After a background survey to determine the yellows most likely to appear in 18th century colonial oil paintings, I set out to establish a sort of database of comparative SERS spectra from known reference yellows.

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